Even in this specific network configuration, the metrics introduced in section  maintain their significance. The relevance of each layer depends, in fact, on the relative number of neighbours in a layer with respect to the multiple degree of the node. In particular, the shape of the connectivity, implemented from the definition proposed in [1]} ensures that the Heel-ness of a node consistently depend on the node's layer relevance and the node's connection redundancy instead that only on the connection intensity. We stress that, if this would have been the case, fully connected layers would have brought to an initial connectivity measure that would have encoded only operational information, i.e. information about the mobility flow passing trough links, for all the nodes that share the same bus lines independently on the possible different size of the disconnected component they might cause after a disruptive event involving one or all of their connections. This highlight the importance of a combined approach that considers both the structure of the multilayer network, i.e. relevance and redundancy of the connections, and the network usage, i.e. the information about mobility flows over different links.
